The present invention relates to a liquid crystal display apparatus displaying black representation, particularly to an in-plane-switching-mode (IPS) liquid crystal display apparatus in which liquid crystal molecules are homogeneously oriented to control transmittance of light by applying a horizontal electric field to the liquid crystal molecules and a great improvement of its viewing angle characteristics (particularly, displaying black representation and low gray levels).
As a method for applying the direction of an electric field to liquid crystal in the direction parallel with a substrate (hereafter referred to as horizontal electric field method or IPS mode), a method using a comb-teeth electrode provided on one substrate is disclosed in JP-B-63-21907, JP-A-9-80424, and JP-A-2001-056476. Because a liquid-crystal molecule rotates mainly in a plane parallel with a substrate, it is known that the difference between birefringence at the time of electric field application and at the time of no electric field application viewed from a diagonal direction is small and the viewing angle is wide.
However, in the IPS mode, it is known that light leaks depending on the characteristic of the polarizer when viewing from a diagonal direction, which is in an orientation deviated from the absorption axis of a polarizer, while a change of the double refraction factor of liquid crystal is small. To eliminate the diagonal light leak of the polarizer, a method for using a retardation film is disclosed in JP-A-2001-350022. However, though this document basically considers the improvement of viewing angle of only a polarizer and influence of liquid crystal for a VA mode, a method for compensating the influence by a liquid crystal layer is not disclosed for the IPS mode.
Moreover, means for solving a problem of a color change of white depending on an observation direction is disclosed in Japanese Patent No. 3204182. However, improvement of black representation characteristic is not described.
Furthermore, Japanese Patent No. 2982869 discloses a configuration for placing a wave plate on one inner side of a polarizer in order to improve the viewing angle characteristic of black display. However, it has been found by our study that though this method considers the influence of a support base material TAC (tri-acetylcellulose) provided on both sides of the polarizer, black does not completely dark at a diagonal viewing angle with phase compensation by one sheet at either side and that the method does not provide a configuration which decreases coloring due to wavelength dispersion in the liquid crystal layer. Moreover, it does not disclose phase compensation differences depending on whether the orientation axis (lag axis) of a liquid crystal molecule at the time of black representation is parallel with or vertical to the polarizer at the incoming side, which is our invention. In the case of the above-described well-known example, the visual-angle characteristic is discussed only by brightness characteristic but the corresponding method to this color change is not disclosed.